I am working with asp.net and try to access through my login form sql serverdatabase mydbwhen logging in as windows user my_pc\xyzuser it fails throwing error :login failed for user my_pc\xyzuser can not access database mydb.user does not exists.what should be done for workaroundconnectionstring is:data source=localhost;integrated security=true;initial catalog=mydb

Sej, Though it's little old post but did you got it rectified ? As the SQL masters told, the error message clearly shows that there is no user created in database level. So you need to create DB user in your database mapping it to the login you created at server level. Thereafter grant the DB level user some permissions and thereafter try. Remember:Step 1: Create login at server level [security at server level is called login]Step 2: Create user at DB level [Login created at Step 1 to be mapped to this new user] Map permissions to this user as per requirement.Step 3 (not mandatory): Repeat Step 2 in each database, in which this new user requires permission.